Billet grinder



July 2, 1957 w. K. LOWE BILLET GRINDER Original Filed April 1, 1952 3Sheets-Sheet l INVENTOR. VIZ/1 A cEKLoM/E. .BYW ATTORNEKS'.

July 2, 1957 w. K. LOWE V 2,79%,532

BILLET GRINDER Original Filed April l, 1952 3' Shets-Sheet 2 Ifij L AM

1:: 1 I l 17 m h l h 'd f". P A57 I 4 INVENTOR.

m LLA cgKLows.

BY MMMM, J 9 MW ATTORNEYS.

United States Patent BILLET GRINDER Original application April 1, 1952,Serial No. 279,789, now

Patent No. 2,726,490. Divided and this application March 23, 1955,Serial No. 496,255

6 Claims. (Cl. 51-45) This invention relates to apparatus forautomatically grinding surfaces of metal billets such as, for example,rolled or forged steel billets.

This application is a division of my application Ser. No. 279,789, filedApril 1, 1952, and now Patent No. 2,726,490, and relates to the billetgrinding apparatus disclosed therein and particularly to controls forsuch apparatus for reducing the pressure of the grinding wheel on thebillet as it approaches the corners thereof to prevent therebyundesirable rounding of the corners.

The objects and advantages of the invention will more fully appear fromthe following detailed description setting fo'rth the manner in which wenow prefer to practice the invention and from the accompanying drawingsin which:

Fig; l is a side elevation view of the preferred embodiment of theinvention and corresponds to Fig. -4 of my United States Patent No.2,726,490;

Fig. 2 is a schematic diagram illustrating the system employed in thepreferred embodiment of the invention for reciprocating a billet and thegrinding wheel and for controlling the load on the grinding wheel; and

Fig. 3 is an electric circuit diagram showing the electrical circuitswhich may be employed for controlling the grinding apparatus of theinvention.

Referring to Fig. 1 which shows a side elevation view of billet.grinding apparatus incorporating the invention and which is describedin detail in my patent abovementioned, it will be seen that a grindingwheel 10 is mounted on a rotatable shaft 11 which is mounted on a pairof bearings which are supported on the endof a beam 14. The grindingwheel 10 is drivingly connected by means of belts 16 to an electricmotor 18.

The motor 18 is secured to a platform 19 which is fastened to the beam14 at a point thereon spaced from thepivot point of the beam 14. Thebeam 14 is pivotally mounted on a frame 20 by means of a shaft 21.

The shaft 21 is rotatably mounted on a pair of plates 60 which areslidably mounted on a pair of shaftswhose axes are parallel to eachother and one of which is shown in Fig. 1 and is identified by thenumeral 32-. The shafts are secured to the frameztl by bolts 34.

It will be noted from the drawings that the grinding wheel 10 and itsassociated driving motor'18 are both mounted on the same side of thepivot shaft 21 and therefore their weight tends to press the beam .14downward at the side of the pivot shaft 21 on which the wheel and motorare mounted. A movable counter-weight 35 and afixed counter-weight 36are provided on the opposite side of the shaft 21 so as tocounter-balance 'the'weight of the wheel 10' and the motor 18. Thecounter-weight 35 is suspended from the beam 14 as described in theabove-mentioned patent.

The counterweight 35 is adjustable along the beam 14 by fluid actuatedcylinder and piston means =43 which comprises a cylinder 44 and a piston'45 and which is mounted on the underside of the bean! 14. The cylin-"ice der 44 is secured to the beam 14 in any suitable manner, such as bya bracket 46, and the piston rod 47 is connected to the counter-weight35 by a pivotal coupling 48. The cylinder has a pair of flexible fluidlines 49 and. 50 for the purpose of admitting fluid to the cylinder andthereby moving the piston rod 47 in either of two directions.

The beam 14 is reciprocated by fluid actuated cylinder and piston means51 comprising a cylinder 52 andta piston 53. The cylinder 52 is securedto the frame 20 by means of a bracket 54. The piston 53 is connected toa piston rod 57 which is secured to the plate 60 as described in theabove-mentioned patent.

A billet to be ground such as billet 61 is mounted on a table 62 whichis movably supported on. rails. and 71 which are mounted on a frame 74.Fluid actuated cylinder and piston means 76 is provided to move thetable 62' back and forth in a direction parallel to' the longitudinalaxis of the billet 61. The cylinder and piston means 76 has a pair offlexible fluid lines (not shown) connected thereto for supplying fluidthereto and for thereby causing the table 62 to move in either of twodirections along the rails 70 and 71.

The billet 61 preferably is clamped on top of the table 62 by airactuated cylinder and piston means described in Patent No. 2,726,490,one portion of which, cylinder and piston means 82, is shown in Fig. l.

A quick-operating, air actuated cylinder and piston means 91 isconnected between the end of beam 14 and the foundation 92. One end ofthe means 91 is pivotally connected to a bracket 93 secured to thefoundation 9 2 by a pin 94, and the piston rod 95 is connected to theend of the beam 14 by a yoke 96, a pin 97 and a bracket 98; Air underpressure is supplied to the means 91 through a hose 99 and is exhaustedfrom the means 91 through the port 160. When the grinding apparatus isin operation the cylinder and piston means 91 is inoperative; that is,it exerts substantially no force on the beam 14 and hence the pressureon the grinding wheel 10 is determined substantially by the position ofthe counterweight 35. However, in the event that it is desired to liftthe grinding wheel 10 quickly either from the billet 61 or because thewheel has overrun the billet, then .air

, under pressure is supplied to the means 911 through the hose 99, andthe end of the beam 14 to which the rod' 95 is attached is moveddownwardly.

In Fig. 2 there is shown schematically the oil operated cylinder andpiston means and their connections both with the valves which produceoperation. thereof and the electrical controls which are operatedthereby. Referring to Fig. 2, oil is supplied under pressure by a motorand a pump 156 from a reservoir 157. The

'oil is conveyed to the cylinder and piston means over the lines 158,159, 169 and 161, line 158. being provided with a pressure relief valve162 and lines 159', 160 and 161 being provided with shut-oh" valves 163,1 614 and 165. The supply of fluid to the cylinder and ,piston means 43,'76 and 51 is controlled respectively by electrically operable valves166, 167 and 163. The value 166 is provided with a ,pair of solenoids169 and. 179 which operate the valve, and pressure relief valves 171 and172 are connected between valve 166 and cylinder and piston means 43.The valves 167 and 1'68 are-also equipped with pairs of solenoids173'-174 and 175 -176, and pressure relief valves 177, 178, 179 and 1.80are connected in the lines between the valves 167 and 1:68 and thecylinders 51 and 76.

The solenoids 169 and of valve 166 are controlled by the circuit shownin Fig. 3 and described in connection therewith, and the valves 167 and1 68 are controlled respectively by the limit switches 181- 182 mountedon the frame 74 to the rear of table 62 (see Fig. 1 and Patent No.2,726,490) and switches 183- 184 mounted on the frame as described inPatent No. 2,726,490. Limit switches 181 and 182 are actuated by a pairof stops 185 and 186 movable with the table 62 and safety lift switches187 and 188 carried by the table 62 are controlled by a pair ofstationary but adjustable stops 189 and 190 as described in Patent No.2,726,490.

Limit switches 183 and 184 are operated by a stop 1 191 carried by thebeam 14 as described in Patent No. 2,726,490. ,Switches 192 and 193 arealso mounted on the frame 20 to the right of the beam 14, as indicatedin Fig. I and are operated by a cam 194 also shown in Fig. 1. Theseswitches 192and 193 are employed in connection with relay 195 to reducethe pressure on the grinding wheel 10 before the wheel reaches thecorners of the billet 61 and their operation will be described ingreater detail in connection with Fig. 3. Relay 195 has contacts 196 and197 and is connected in series with the switches 192 and 193 and thesource 198.

A limit switch 199 is mounted on the end of beam 14, as is best shown inFig. l, and is engageable with the bracket 37 which supports thecounter-weight so as to deenergize the solenoid 169 when thecounter-weight 35 is at its rearmost position.

Referring to Fig. 3, which is an electrical circuit diagram of theelectrical system employed for controlling the grinding apparatus of theinvention, it will be seen that the motor 18 is connected to athree-phase source n through contacts 200 which are controlled by themanually operable switches 201 and 202. The force applied to thegrinding wheel 10 to hold it against the billet 61 is automaticallyadjusted in accordance with the load on the grinding wheel 10. thecircuit shown in the upper left-hand side of Fig. 3. A transformer 203,which may be, for example, a current transformer, is coupled to theinput circuit of the motor 18 and when the motor 18 is in operation avoltage is produced across the secondary of the transformer 203 which isshunted by a reactance 204, a manually variable resistor 205 in serieswith a fixed resistor 206 and the primary 207 of the transformer 208.The secondary 209 of the transformer 208 is connected to diagonallyopposite points on a bridge rectifier 210 which comprises dry rectifiers211, 212, 213 and 214, which may, for example, be selenium or copperoxide rectifiers.. The output of the bridge rectifier 210 is connectedto the energizing coil 215 of a three-position relay 216 which may beshunted by a filter condenser 217. The relay 216 has two pairs ofcontacts 218-219 and 220-221 and an armature 222. The armature 222 isconnected to an adjustable spring 223 which causes the armature 222 toconnect the contacts 20 and 221 unless the coil 215 is energized to atleast a predetermined extent by the rectifier 210. Thus, when only asmall current is flowing through the coil 215, the contacts 220 and 221are connected together by the armature 222, but when the current exceedsa predetermined level, determined by the sensitivity of the relay 216and the tension on the spring 223, contacts 220 and 221 aredisconnected. As the current through coil 215 is further increased, thearmature 222 moves toward the contacts 218 and 219 until finally when asecond predetermined current level is reached the contacts 218 and 219are connected together.

When the handle 224 of the variable resistor 205 is in the verticalposition shown, the contacts 225 and 226 are connected together by thecontactor 227 which is moved into its downward position by the actuator228 on the end of the handle 224 and the contacts 229 and 230 areconnected together by the contactor 231, but when the handle 224 ismoved from the vertical position shown to some position such as the oneshown in dotted lines the contacts 225 and 226 are disconnected and thecontacts 232 and 233 are connected together by the contactor Toaccomplish this, I employ 231. In the vertical position of the handle224 the automatic operation of the grinding apparatus is discontinuedand the grinding wheel 10 is completed lifted off the billet 61, butwhen automatic operation is desired, the handle 224 is moved to the leftfrom the vertical position shown in solid lines to the position shown indotted lines and the contacts 218 and 220 are thereby connected toterminal B of the power source.

Contact 219 is connected to one end of the solenoid or coil 169 employedto actuate the valve 166 and the opposite end of solenoid 169 isconnected to terminal A. Also, contact 221 is connected to one end ofsolenoid or coil which operates the valve 166 in the opposite directionand the other end of solenoid 170 is connected to the terminal A. Thus,when contacts 218 and 219 are connected together by the armature 222, acircuit for the solenoid 169 which actuates the valve 166 in such adirection that the counter-weight 35 is moved rearwardly of the beam 14,and hence in such a direction that the force on the grinding wheel 10 isdecreased, is established from terminal B of the power source throughcontacts 232 and 233 which have been connected by operation of thehandle 224 to the position shown in dotted lines as described above,contactor 231, contacts 218 and 219, solenoid 169 and back to terminalA. However, when contacts 220 and 221 are connected together by armature222, a circuit is completed for energizing solenoid 170 (which moves thecounter-weight 35 toward the grinding wheel 10) from terminal B throughcontacts 232 and 233, contactor 231, contacts 220 and 221, solenoid 170and back to terminal A. When the armature 222 is in a positionintermediate the contacts 220-221 and 2 18-219, neither of the pairs ofcontacts is connected together and hence neither of the solenoids 169and 170 is energized. When neither solenoid 169 and 170 is energized,the counter-weight 35 remains in a fixed position.

Since the current in coil 215 varies with the current in the inputcircuit of the motor 18, the position of the counter-weight 35 iscontrolled by the current in the input circuit of motor 18 and hence bythe energy consumed by the motor 18. Consequently, when the inputcurrent to the motor 18 is increased above a predetermined value becauseof an increase in the load on the grinding wheel 10, the valve 166 isoperated so that the counter-weight 35 moves away from the grindingwheel 10. Also, when the input current to the motor 18 decreases below apredetermined value because of a decrease in the load on the grindingwheel 10, the valve 166 is operated so that the counter-weight movestoward the grinding wheel 10. In this manner, the load on the motor 18,and hence the rate at which material is removed from the billet 61, andthe load on the grinding Wheel 10 may be maintained at a substantiallyconstant value.

The value of the load on the motor 18 may be adjusted by adjustment ofthe spring 223 and by adjustment of the position of the handle 224.Because of the well-known characteristics of a current transformer,variations of the load on the output winding of the transformer 203 willcause corresponding variations in the output voltage of the transformer203. Adjustment of the handle 224 changes the value of the resistor 205in series with the resistor 206 and hence changes the load on thetransformer 203 and the voltage of the primary 207 at the transformer208. Thus, if the handle 224 is moved to the position shown in dottedlines, the value of the resistor 205 is decreased causing an increase inthe load on the transformer 203 and the voltage at the primary winding207 is correspondingly decreased. When the handle 224 is slightly to theleft of the vertical position shown, the resistor 205 has the maximumvalue that can be attained under automatic operating conditions andhence the voltage at the primary winding 207 is at its maximum valueunder these conditions. The current in the coil 215 changes with and inthe same direction as the voltage across the primary winding 207.

In accordance with the invention, the downward force on the grindingwheel is reduced as the grinding wheel 10 approaches the forward andrear corners of the billet 61. Thisfeature is desirable not only becauseit prevents sudden dropping of the grinding wheel if it goes over thefront and rear corners of the billet 61, but also because it reducesrounding of these corners of the billet. Adjustable resistor 234, relay195 and its associated armature 235 and contact 196 and switches 192 and193 are provided to accomplish this control of the force on the grindingwheel 10.

Referring to Fig. l, the switches 192 and 193 which are adjustablymounted on the frame 20 are adjusted to such positions that switch 192is operated by cam 194 when the billet contacting surface of thegrinding Wheel 10 is closeto the forward edge of the billet 61 and theswitch 193 is operated by the cam 194 when the billet contacting surfaceof the grinding wheel 10 is close to the rear corner of the billet 61.As appears in Fig. 3, the relay 195 normally is energized by .a circuitwhich may be traced from terminal A through switches .192 and 193,through the coil of relay 195 and back to terminal B. When the relay 195is energized, the armature 235 is pulled up against contact 196 andhence the resistor 234 is shorted out. With resistor 234 shorted out,the load on the transformer 203 and therefore the voltage at the primarywinding 207 is determined by the setting of handle 224 and resistor 206and hence the downward force on the grinding wheel 10 is determined bythe setting of the handle 224. However, when either of the switches 192and 193 is operated by the cam 194, the energizing circuit for relay 195is broken and the armature 235 falls back against contact 197. Theresistance then appearing between the leads 237 and 238 is increased bythe value of the resistance 234. Because of the increase of resistancebetween leads 237 and 238 and the consequent decrease of the load on thetransformer 203 a larger voltage will appear across the primary 207 thanwhen the resistor 234 is shorted out. A larger voltage across theprimary 207 produces a larger current in the coil 215 and pulls armature222 against contacts 218 and 219 closing the circuit for the solenoid169 which, as explained previously, moves the counter-weight 35rearwardly away from the grinding wheel 10 and reduces the downwardforce on the grinding wheel 10. As soon as the counter-weight 35 hasmoved rearwardly enough to reduce the downward force on the grindingwheel 10, and hence the input current to the motor 13, an .amountsufiicient to compensate for the increase in current produced in coil215 by the insertion of the resistor 234 in series with resistors 205and 206, the armature 222 will resume its intermediate position and thecounter-weight 35 will stop. It is thus apparent that when either of theswitches 192 and 193 is operated, the downward force of the grindingwheel 10 is decreased and the amount of decrease is determined by thesetting of control 239 for resistor 234.

It will also be apparent from a consideration of the above and from anexamination of the circuit diagram in Fig. 3 that the downward force onthe grinding wheel 10 may be manually adjusted at any time during theoperation of the grinding apparatus by movement of the handle 224. Inits position nearest the horizontal in the counter-clockwise direction,the handle will reduce the voltage across the primary 207 to the minimumfor a predetermined value of the current supplied to the motor 18.Therefore, in order to separate armature 222 from the contacts 220 and221, a higher motor current will be required, and the counter-Weight 35will cause the wheel 10 to press with maximum force against the billet61 and, as the handle 224 is moved toward the vertical position shown insolid lines, the downward force is decreased until in some position justprior to the verticalposition the minimum force which it is possible'toobtain with an automatic control circuit is applied to-the grindingwheel 10. However, the circuit shown is so arranged that by motion ofthe handle 224 into its vertical position the counter-weight 35 is movedto the rear end of the beam 14'. When the counter-weight 35 is at therear end of thebeam 14, the wheel 10 is completely lifted from thebillet 61, and normally the grinding wheel is in this position when thegrinding apparatus is idle. Therefore, it is desirable that when thecounter-weight 35 is in its rearmost position, the solenoid 169 isdeenergized. To accomplish this result the arm 228 -on the handle 224moves contactor 227 against contacts 225 and 226, connecting contacts225 and 226 together, and the arm 228 permits the con'tactor 231 toconnect contacts .229 and 230 together. Thus, a circuit may be tracedfrom terminal B through contacts 229 and 230, contac'tor 231, switch199, contacts 225 and 226, contactor 227, solenoid169 and back toterminal A, and when the handle 224 is first moved to the verticalposition, the solenoid 169 is energized causing the counterweight 35 tomove rearwardly along the beam 14. However, when the counter-weight 35reaches its rearmost position, it operates switch 199 and opens thelastmentioned energizing circuit for solenoid 169. The counterweight 35remains in the rearmost position until the handle 224 is again movedfrom its vertical position and places the counter-weight 35 under theautomatic control circuit previously described.

Solenoids 173 and 174 which control the operation of valve 167, andhence the reciprocation of the table 62, may be energized throughmanually operable switches 240 and 241, through conta'ctor 242 rotatableby motor 243 and through the table controlled switches 181 and 182.Switches 240 and 241 are provided in the event that it is desired tocontrol the reciprocation of the table 62 manually and the switches 181and 182 are provided for automatic control of the table reciprocation,such switches being operated as described in Patent No. 2,726,490.

if there is a portion of the surface of the billet 61 which requiresadditional grinding, a relatively "short reciprocatory strokeof thetable may be provided by operation of the timer control switch 24-5 andthe control 246 on the timer motor speed control apparatus 247, thelatter apparatus being connected to the motor 243 and used't'o controlthe speed thereof. Operation of the switch 245 supplies electricalenergy to the contactor 242 which alternately energizes solenoids 173and 1'74 and the speed of the motor 243 as adjusted by the control 246determines the times at which solenoids 1'73 and 174 are alternatelyenergized and hence the length of the path of movement of the table 62.

Switches 248 and 249 are provided for manual control of thereciprocation of the beam 14, and switches 183' and 184, as indicatedpreviously, provide automatic control of the reciprocation of the beam14 in the manner described in Patent No. 2,7 26,490.

A manually operable switch 250 is provided so that switches 131, 182,133 and 184 may be disabled when it is desired to stop the automaticreciprocation of the beam 14 and the table '62. With switch 250 in its011 position the manual switches 240, 241, 248 and 249 may be employedto position the beam 14 or the table 62.

The billet turning solenoid or coil which controls the turning of thebillet 61 as described in Patent No. 2,726,490 may be energized byoperation of the manually operable switch 251.

The safety lift solenoid or coil 142 which controls the supply of air tocylinder and piston means 91 may be energized by the switches 187 and188 which are mounted and operated as described in Patent No. 2,726,490and it maybe energized by the manually operable switch 252. It thewheel10 passes beyond the end of a billet one of theswitches 187 and 188 is operated and energizes relay 253 which has armatures 254 and 255and contacts 256 and 257. When relay 253 is energized it pulls armature254 against contact 256 and armature 255 against contact 257. Engagementof the armature 255 with the contact 257 closes an energizing circuitfor the relay 253 and keeps the relay 253 operated until the relay isreset by the switch 252, as indicated hereinafter. Armature 254, whenpulled against the contact 256, closes an energizing circuit for thesolenoid 142 and hence causes operation of the air actuated cylinder andpiston means 91. As previously described, the air actuated cylinder andpiston means 91 pulls the rear of the beam 14 down- \vardly and liftsthe wheel 10 off the billet 61.

If one of the switches 187 and 188 is operated, the cylinder and pistonmeans 91 remains operated as long as the relay 253 is energized. Becauseof the holding circuit through armature 255 and contact 257, the relay253 remains energized until switch. 252 is operated to its resetposition in which the contacts 258 and 259 are connected together. Whencontacts 258 and 259 are con nected together, the relay 253 isshort-circuited and the armatures 254 and 255 fall back against theiridle contacts.

If at any time it becomes necessary to lift the wheel 10 quickly fromthe billet 61, the manually operable switch 252 may be operated to itslift position so as to connect contacts 260 and 261 together. Operationof the switch 252 in this manner also energizes the safety lift solenoid142 and actuates the cylinder and piston means 91. However, as soon asthe switch 252 is returned to its intermediate or rest position, thesolenoid 142 is deenergized and cylinder and piston means 91 becomesidle.

Transformer 262 is provided for the purpose of supplying the requiredvoltage to the relay 253 and may be ommited if a relay operating at thevoltage of the source connected to terminals A-B is employed.

From the above it will be seen that when the appropriate switches areoperated the table 62 is reciprocated along a path which is parallel tothe axis of the grinding wheel 10 and the grinding wheel 10 isreciprocated crosswise of the table 62. The rate at which the table 62and the beam 14 are reciprocated may be controlled by control of thepressure of the fluid supplied to the cylinders 76 and 43 and bycontrolling the rate at which the fluid is supplied to these cylinders.In the preferred form of the invention the grinding wheel 10 and thebeam 14 are moved at a relatively slow rate and the table 62 is moved ata relatively rapid rate so that the table 62 is moved back and forthseveral times during the time it takes the grinding wheel 10 to movefrom the rear corner of the billet 61 to the front corner of the billet61.

Once the switches 183, 184, 192, 193, 181 and 182 have been set to thepositions described above, the grinding wheel 10 will completelytraverse the surface of a billet one or more times without any action onthe part of an operator. When the surface of a billet has been ground tothe desired extent, the automatic reciprocation of the table 62 and thebeam 14 is discontinued, and the billet is unclamped, turned andreclamped so that a new surface of the billet may be ground by a similaropera tron.

Although we have illustrated and described the load controllingapparatus of the invention in connection with a grinding wheel that ismounted on a pivotally mounted beam, it will be apparent that suchcontrolling apparatus may also be used to control the load on a grindingwheel mounted in other ways. Also, it will be apparent to those skilledin the art that the stops and limit switches for controlling thereciprocation of the beam 14 and the table 62 and for controlling thelifting of the grinding wheel 10 may be differently arranged.

Having thus described the invention with particular reference to thepreferred form thereof, it will be obvious to those skilled in the artto which the invention pertains, after understanding the invention, thatvarious changes and other modifications may be made therein withoutdeparting from the spirit and scope of the invention, as defined by theclaims appended hereto.

I claim:

1. Grinding apparatus comprising a table for holding a piece to beground, means for mounting a grinding wheel, means for reciprocatingsaid mounting means in a predetermined path, means for applying a forceto said mounting means in the direction of said table and for adjustingthe force on said mounting means and means actuatable by said means forreciprocating said mounting means for operating said force applying andadjusting means in a direction which reduces said force from a firstpredetermined value to a second predetermined value greater than zero.

2. Grinding apparatus comprising a table for holding a piece to beground, means for reciprocating said table connected to said table,means for mounting a grinding wheel adjacent said table, a grindingwheel on said mounting means, means for reciprocating said mountingmeans in a predetermined path connected to said mounting means, meansfor applying a force in the direction of said table and for adjustingthe force on said mounting means, whereby the pressure of said grindingwheel against said piece may be controlled, and means for operating saidadjusting means in a direction to effect a reduction in the pressure ofsaid wheel against said piece while maintaining said wheel in contactwith said piece, said operating means being actuatable by said means forreciprocating said mounting means in at least one predetermined positionthereof.

3. Grinding apparatus comprising a table for holding a piece to beground, a grinding wheel, means mounting said grinding wheel adjacentsaid table, means for reciprocating said mounting means connected tosaid mounting means, means for adjusting the pressure of said grindingwheel against said piece connected to said mounting means, control meansconnected to said adjusting means for varying the pressure of saidgrinding wheel on said piece in accordance with the load on saidgrinding wheel and means for reducing said pressure by a predeterminedamount connected to said control means, the reduced value of saidpressure being greater than zero and said reducing means beingactuatable by said reciprocating means in a predetermined positionthereof.

4. Grinding apparatus comprising a table for holding a piece to beground, a grinding wheel, means mounting said grinding wheel adjacentsaid table, means for reciprocating said mounting means connected tosaid mounting means, means for adjusting said mounting means withrespect to said piece whereby the pressure of said grinding wheelagainst said piece may be adjusted and means for reducing the pressureof said grinding wheel against said piece while maintaining said wheelin contact with said piece comprising means actuatable by saidreciprocating means in a predetermined position thereof and connected tosaid adjusting means, said means actuatable by said reciprocating meansbeing adapted to operate said adjusting means a predetermined amount onactuation by said reciprocating means.

.5. Grinding apparatus comprising a table for holding a piece to beground, means for reciprocating said table, means for mounting agrinding wheel, means for reciprocating said mounting means in apredetermined path, means for applying force on said mounting means inthe direction of said table and for adjusting said force, and meansactuatable by said means for reciprocating said mounting means in apredetermined position thereof intermediate the ends of said path foroperating said force applying and adjusting means in a direction whichreduces said force.

6. Grinding apparatus comprising a table for holding a piece to beground, means for reciprocating said table, means for mounting agrinding wheel, means for reciproeating said mounting means in apredetermined path, References Cited in the file of this patent meansfor applying force On said mounting means in the UNITED STATES PATENTSdirection of said table and for adjusting said force, and

means actuatable by said means for reciprocating said 2154252 sh'llkofi11, 1939 mounting means in two predetermined positions thereof 5 2445433Holmstrom July 1948 adjacent the ends of said path but spaced from saidends FOREIGN PATENTS for operating said force applying and adjustingmeans in 221,029 Great Britain sept- 24 1924 a direction which reducessaid force. 363,544 Great Britain D cc. 24, 1931

